Alkoxy acyl halides, preparation

The availability of amino-substituted furazans, both by direct synthesis from aminogly-oximes and via Hofmann degradation of the corresponding carboxamides, allows urea, thiourea, imino and acylamido derivatives, for example, to be prepared by reaction with isocyanates, isothiocyanates, aldehydes and acyl halides, respectively (73JPR791, 77JCS(P1)1616). Alkoxy and acyloxy derivatives are likewise formed from hydroxyfurazans (79JHC689). 

The reactions of the homocyclic ring of benzofuroxans, which are described in detail in Section 4.22.3.3, provide access to numerous derivatives. Nucleophilic displacement of halides is facile when activating nitro groups are present, allowing alkoxy, aryloxy, thio and amino groups to be introduced. Electrophilic substitutions, e.g. nitration, are also valuable. Further transformations may also be performed on benzo-ring substituents. Such modifications include acetoxy to hydroxy acetamido to amino and acyl halides to esters and amides. Some reactions of the substituents of monocyclic furoxans allow hetero-substituted analogues of benzofuroxans to be prepared. For example, pyridazinofuroxans are formed by condensation of diacylfuroxans with hydrazine. 

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